Compositions, methods and apparatuses for preserving platelets

ABSTRACT

A platelet composition suitable for direct transfusion into a patient is provided. The platelet composition includes a preservation medium comprising plasma and a gel-forming material in a concentration relative to the plasma such that the medium is in a sufficiently fluent state at about 37° C. to allow platelets to move within the medium and is in a sufficiently gelatinous state at about 5° C. to substantially prevent platelets from moving freely within the medium; and platelets.

RELATIONSHIP TO COPENDING APPLICATION

[0001] This application is a continuation-in-part of U.S. applicationSer. No. 09/183,581, filed Oct. 30, 1998 entitled “METHOD AND APPARATUSFOR PRESERVING BIOLOGICAL MATERIALS”, which is incorporated herein byreference.

FIELD OF THE INVENTION

[0002] The present invention relates to compositions, methods andapparatuses for preserving biological materials. More particularly, theinvention relates to compositions, methods and apparatuses for theextended storage of platelets.

BACKGROUND OF THE INVENTION

[0003] Over the last 40 years the need for the therapeutic use ofbiological materials, such as blood, skin and other tissues, kidneys,hearts, livers and other body organs has increased dramatically. Bloodand plasmas components, including red cells, platelets, clottingfactors, albumin, and antibodies are isolated and used to treat variousbleeding problems. In particular, platelets, essential components of thehuman blood, are used extensively for assisting in the control ofbleeding and replacing functionally defective platelets in patients. Forexample, platelet transfusions are required by trauma patients who havelost significant amount of blood, patients undergoing chemotherapy thatreduces the number of platelets and causes functional defects inremaining platelets, and patients with certain platelet-depletingdiseases.

[0004] Constituents in whole blood include leukocytes (white bloodcells), erythrocytes (red blood cells), thrombocytes, platelets andplasma. Platelets are not entire cells but small detached cell fragmentsor “minicells” derived from the cortical cytoplasm of large cells calledmegakaryocytes in the bone marrow. Platelets comprise an outer membraneand cytoplasm from the megakaryocytes which contain granules, densebodies, dense tubular system and mitochondria. Platelets adherespecifically to the endothelial cell lining of damaged blood vessels,where they trigger and participate in hemostasis, or clotting, andrelease inflammatory mediators in response to contact with theendothelial cell lining. Important mediators released by plateletsinclude serotonin and coagulation factors. Vascular breaches arerepaired by platelets through adhesion and the response to damage isamplified by platelet secretions resulting in platelet aggregation andfibrin formation, i.e. stabilized clot.

[0005] It is very important to preserve platelets after their isolationfrom the body under conditions not only maintaining the biologicalactivity of platelets but also suitable for clinical use. The averagesurvival time for a platelet in the body after it leaves the bone marrowis 8-10 days. The average expected survival time for circulatingplatelets is 4-5 days, an average of the entire population. The averagesurvival time for platelets after isolation from the body is about 5days at room temperature.

[0006] The current standard and approved method for platelet storage isin a platelet bag at room temperature and limited to five days. Thestorage time is presumably limited by a decrease in pH due to increasedlactate associated with anaerobic metabolic activity. Furthermore, thebag of platelets in plasma must be constantly in motion on a rocker toprevent aggregation. One of the disadvantages associated with preservingplatelets under room temperature is the growth of bacteria in theplatelet suspension. Platelets in a suspension stored in a refrigerator,albeit with suppressed bacteria growth, tend to activate upon contactingeach other and aggregate.

[0007] Several approaches such as cryopreservation (freezing) techniqueshave yielded an increased number of platelets following storage.However, there is a limitation in the functional capacity andpersistence of platelets in circulation that are recovered from suchpreservation conditions by using these methods. Freezing temperaturesrequire the use of cryoprotectors such as DMSO (dimethyl sulfoxide)(Valeri, Feingold, and Marchionni, Blood, vol. 43, No. 1 (January)1974)and THROMBOSO™ to prevent damage to these biological materials. However,these cryoprotectors are cytotoxic, and typically leave a significantportion of the platelets with either reduced or no functional ability.Moreover, cryoprotectors usually require time-consuming preparation,such as rinsing processes, before the materials can be used, andcryoprotector residues often still remain afterwards. Freezing processescan store erythrocytes for more than 30 days, and leukocytes up to 12hours only.

[0008] Other attempts to preserve platelets have included addingplatelets activation inhibitors (Bode, Holme, Heaton and Swanson, VoxSang, 60: 105-112 (1991); U.S. Pat. No. 5,622,867) or gelatin into thepreservation medium (U.S. Pat. No. 2,786,014).

[0009] A need continues to exist for a storage system that will storebiological materials, particularly platelets, for an extended period oftime and still maintains their viability and bioactivity.

SUMMARY OF THE INVENTION

[0010] The present invention relates to compositions, methods andapparatuses for the extended storage of biological material and, inparticular, platelets.

[0011] According to one embodiment, a platelet composition suitable fordirect transfusion into a patient is provided comprising: a preservationmedium comprising plasma and a gel-forming material in a concentrationrelative to the plasma such that the medium is in a sufficiently fluentstate at a first temperature to allow platelets to move within themedium and is in a sufficiently gelatinous state at a second, lowertemperature to substantially prevent platelets from moving freely withinthe medium; and platelets.

[0012] According to this embodiment, the first temperature is preferablyabout 37° C. and the second temperature is preferably about 5° C.

[0013] According to another embodiment, a platelet composition suitablefor direct transfusion into a patient is provided comprising: apreservation medium comprising plasma and a gel-forming material in aconcentration relative to the plasma such that the medium is in asufficiently fluent state at a first temperature to allow platelets tomove within the medium and is in a sufficiently gelatinous state at asecond, lower temperature to substantially prevent platelets from movingfreely within the medium; and platelets which have been stored withinthe preservation medium in a gelatinous state for at least 3 days whereat least 50% of the platelets are intact and functional after the atleast 3 days.

[0014] According to this embodiment, the first temperature is preferablyabout 37° C. and the second temperature is preferably about 5° C.

[0015] Also according to this embodiment, the platelets may be storedwithin the preservation medium for at least 5 days, more preferably atleast 7 days. Also according to this embodiment, the platelets may bestored within the preservation medium for between 3 and 20 days, morepreferably between 5 and 20 days. Longer storage of platelets is alsopossible.

[0016] Also according to this embodiment, the platelets may be storedwithin the preservation medium at a temperature less than 10° C. andpreferably between −10° C. and 10° C. In one variation, the plateletsare stored at a temperature between 0° C. and 10° C. at 1 ATM, morepreferably at a temperature between 0° C. and 5° C. at 1 ATM. In anothervariation, the platelets are stored within the preservation medium at atemperature between −10° C. and 0° C. at a pressure greater than 10 ATM,more preferably at a temperature between −8° C. and −2° C. at a pressuregreater than 10 ATM.

[0017] According to another embodiment, a platelet composition suitablefor direct transfusion into a patient is provided comprising: apreservation medium comprising plasma and a gel-forming material in aconcentration relative to the plasma such that the medium is in asufficiently fluent state at a first temperature to allow platelets tomove within the medium and is in a sufficiently gelatinous state at asecond, lower temperature to substantially prevent platelets from movingfreely within the medium; and platelets which have been stored withinthe preservation medium in a gelatinous state for at least 1 day at apressure of at least 10 ATM and a temperature below 0° C. where at least50% of the platelets are intact and functional after the at least 1 day.

[0018] According to this embodiment, the first temperature is preferablyabout 37° C. and the second temperature is preferably about 5° C.

[0019] Also according to this embodiment, the platelets may be storedwithin the preservation medium at a pressure of at least 30 ATM, morepreferably at least 70 ATM, most preferably at least 200 ATM.

[0020] According to this embodiment, the platelets may be stored withinthe preservation medium for at least 3 days, more preferably at least 5days and most preferably at least 7 days. Also according to thisembodiment, the platelets may be stored within the preservation mediumfor between 2 and 20 days, more preferably between 3 and 20 days. Longerstorage of platelets is also possible.

[0021] The present invention also relates to a variety of methods forstoring platelets for direct transfusion into a patient. In oneembodiment, the method comprises:

[0022] forming a fluent platelet composition comprising platelets and apreservation medium including plasma and a gel-forming material in aconcentration relative to the plasma such that the medium is in asufficiently fluent state at a first temperature to allow platelets tomove within the medium and is in a sufficiently gelatinous state at asecond, lower temperature to substantially prevent platelets from movingfreely within the medium;

[0023] cooling the fluent preservation medium to form a sufficientlygelatinous state to substantially prevent free movement of the plateletswithin the preservation medium; and

[0024] storing the platelets within the preservation medium in agelatinous state for at least 3 days where at least 50% of the plateletsare intact and functional after the at least 3 days.

[0025] According to this embodiment, the first temperature is preferablyabout 37° C. and the second temperature is preferably about 5° C.

[0026] According to this embodiment, the platelets may be stored withinthe preservation medium for at least 5 days, more preferably at least 7days. Also according to this embodiment, the platelets may be storedwithin the preservation medium for between 3 and 20 days, morepreferably between 5 and 20 days. Longer storage of platelets is alsopossible.

[0027] Also according to this embodiment, the platelets may be storedwithin the preservation medium at a temperature less than 10° C. andpreferably between −10° C. and 10° C. In one variation, the plateletsare stored at a temperature between 0° C. and 10° C. at 1 ATM, morepreferably at a temperature between 0° C. and 5° C. at 1 ATM. In anothervariation, the platelets are stored within the preservation medium at atemperature between −10° C. and 0° C. at a pressure greater than 10 ATM,more preferably at a temperature between −8° C. and −2° C. at a pressuregreater than 10 ATM.

[0028] According to another embodiment, a method is provided for storingplatelets for direct transfusion into a patient comprising:

[0029] forming a fluent platelet composition comprising platelets and apreservation medium including plasma and a gel-forming material in aconcentration relative to the plasma such that the medium is in asufficiently fluent state at a first temperature to allow platelets tomove within the medium and is in a sufficiently gelatinous state at asecond, lower temperature to substantially prevent platelets from movingfreely within the medium;

[0030] cooling the fluent preservation medium to form a sufficientlygelatinous state to substantially prevent free movement of the plateletswithin the preservation medium; and

[0031] storing the platelets within the preservation medium in agelatinous state for at least 1 day at a temperature below 0° C. and ata pressure of at least 10 ATM where at least 50% of the platelets areintact and functional after the at least 1 day.

[0032] According to this embodiment, the first temperature is about 37°C. and the second temperature is about 5° C.

[0033] According to this embodiment, the platelets are preferably storedwithin the preservation medium at a pressure of at least 30 ATM, morepreferably at a pressure of at least 70 ATM, most preferably at apressure of at least 200 ATM.

[0034] According to this embodiment, the platelets may be stored withinthe preservation medium for at least 3 days, more preferably at least 5days, most preferably at least 7 days. Also according to thisembodiment, the platelets may be stored within the preservation mediumfor between 3 and 20 days, more preferably between 5 and 20 days. Longerstorage of platelets is also possible.

[0035] In regard to all of the above compositions and methods, itpreferred that at least 65% of the platelets are intact and functionalafter storage, more preferably at least 75% of the platelets, mostpreferably at least 85% of the platelets.

[0036] Also in regard to all of the above compositions and methods, thegel-forming material preferably constitutes between 0.2% and 4% of thepreservation medium although the concentration may vary depending on theparticular gel-forming material used. Examples of gel-forming materialthat may be used include, but are not limited to gelatin, agarose, agar,pectin, carob cassia and natural or synthetic water soluble gum such asxanthan gum, konjac gum, guar gum, gum arabic, sodium alginate,carrageenan, irgacanth gum and hydroxyethyl methacrylaic.

[0037] Also in regard to all of the above compositions and methods, thepreservation medium may further include an energy source. The energysource preferably constitutes between 0 and 5% of the preservationmedium, more preferably between 0.25 and 5% of the preservation medium,and most preferably between 0.5 and 5% of the preservation medium. Awide variety of energy sources may be used. Most typically, the energysource is a carbohydrate, such as a sugar. Particular examples of energysources include glucose, sucrose, mannose, fructose and galactose.

[0038] Also in regard to all of the above compositions and methods, thepreservation medium may further include water soluble salts. The saltpreferably constitutes between 0 and 2% of the preservation medium.Examples of salts include, but are not limited to sodium chloride,potassium chloride, magnesium chloride, sodium phosphate, potassiumphosphate and sodium gluconate.

[0039] Also in regard to all of the above compositions and methods, thepreservation medium may further include an anticoagulant. Examples ofanticoagulants that may be used include heparin, citrate dextrose,citrate phosphate dextrose, amantadine, ajoene and ticlopidine.

[0040] Also in regard to all of the above compositions and methods, thepreservation medium may further include amino acids. Examples of aminoacids that may be used include arginine, lysine, aspartate andglutamate.

[0041] The present invention also relates to an apparatus for preservingbiological materials. In one embodiment, the apparatus includes achamber having a mouth and a lip, the lip having an inside surface and atop surface, the inside surface and the top surface of the lip meetingat a first radius, the top surface of the lip having a channel. Theapparatus also includes a cover configured to mate with and seal thechamber, the cover having a bottom surface, the bottom surface having aprotrusion and a sealing structure, the bottom surface of the cover andthe protrusion meeting at a second radius, the protrusion being insertedinto the mouth of the chamber when the cover is mated with the chamber,the protrusion having a side surface, the side surface of the protrusionand the inside surface of the lip defining a first gap and beingsubstantially parallel when the cover is mated with the chamber, thebottom surface of the cover and the top surface of the lip defining asecond gap and being substantially parallel when the cover is mated withthe chamber, the second gap having a length greater than a width of thefirst gap, the sealing structure being inserted into the channel of thelip when the cover is mated with the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042]FIG. 1 shows a graph of In K versus temperature for rate ofbiochemical reaction.

[0043]FIG. 2 the phase transition lines for plasma and a 2.5% NaClsolution.

[0044]FIG. 3 shows another set of phase transition lines.

[0045]FIG. 4 shows a cross-sectional view of a biological materialpreservation apparatus of the present invention.

[0046] FIGS. 5A-5B shows a side cutaway and top views, respectively, ofthe chamber of the preservation apparatus.

[0047]FIG. 6 shows a side view of the cover of the preservationapparatus.

[0048] FIGS. 7A-7C show a cover retaining device of the preservationapparatus.

DETAILED DESCRIPTION OF THE INVENTION

[0049] The present invention provides compositions, methods andapparatuses for storing biological materials and, in particular,platelets, for an extended period of time. According to the presentinvention, functionally intact platelets can be recovered at high yieldsand used directly for platelet transfusions clinically.

[0050] 1. Platelet Composition

[0051] The present invention provides various platelet compositionssuitable for direct transfusion into a patient. According to oneembodiment, a platelet composition comprises: a preservation mediumcomprising plasma and a gel-forming material in a concentration relativeto the plasma such that the medium is in a sufficiently fluent state ata first temperature to allow platelets to move within the medium and isin a sufficiently gelatinous state at a second, lower temperature tosubstantially prevent platelets from moving freely within the medium;and platelets.

[0052] According to this embodiment, the first temperature is preferablyabout 37° C. and the second temperature is preferably about 5° C.

[0053] Platelets tend to activate upon contacting each other andaggregate. When a gel-forming material is added into a suspension ofplatelets in plasma, the resulted platelet preservation medium is in asufficiently fluent state such that the platelets can move anddistribute discretely within the medium following moderate agitations.When the platelet composition is cooled, the gel-forming material causesthe preservation medium to become sufficiently gelatinous so as to forma physical barrier between the already distributed platelets. In thisregard, platelets are prevented from moving freely within the gelatinousmedium. The gelatinous medium also provides a structural support thatmaintains platelet morphology and minimizes deformation of the plateletmembrane when the interior volume of the platelet changes during thecooling process. The gelatinous medium also lowers platelet metabolismby decreasing biochemical exchanges between the platelet and itsenvironment. Inclusion of plasma in the preservation medium is believedto enhance platelet survival by simulating the platelet's nativeenvironment. Thus, retention of the functional integrity of platelets isimproved under the storage conditions provided by the present invention.As a result, a higher percentage of the platelets can still performtheir biological functions, such as promoting blood clotting, afterbeing stored according to present invention.

[0054] The shelf-life of platelets may be successfully extended bystoring the platelets in the preservation medium in a gelatinous state.The platelets may be stored within the preservation medium for at least3 days, more preferably at least 5 days, and most preferably at least 7days where at least 50% of the platelets are intact and functional afterthe storage period.

[0055] Also according to this embodiment, the platelets may be storedwithin the preservation medium for between 3 and 20 days, morepreferably between 5 and 20 days. Longer storage of platelets is alsopossible.

[0056] Also according to this embodiment, the platelets may be storedwithin the preservation medium at a temperature less than 10° C. andpreferably between −10° C. and 10° C. In one variation, the plateletsare stored at a temperature between 0° C. and 10° C. at 1 ATM, morepreferably at a temperature between 0° C. and 5° C. at 1 ATM. In anothervariation, the platelets are stored within the preservation medium at atemperature between −10° C. and 0° C. at a pressure greater than 10 ATM,more preferably at a temperature between −8° C. and −2° C. at a pressuregreater than 10 ATM.

[0057] According to another embodiment, a platelet composition suitablefor direct transfusion into a patient is provided comprising: apreservation medium comprising plasma and a gel-forming material in aconcentration relative to the plasma such that the medium is in asufficiently fluent state at a first temperature to allow platelets tomove within the medium and is in a sufficiently gelatinous state at asecond, lower temperature to substantially prevent platelets from movingfreely within the medium; and platelets which have been stored withinthe preservation medium in a gelatinous state for at least 1 day at apressure of at least 10 ATM and a temperature below 0° C. where at least50% of the platelets are intact and functional after the at least 1 day.

[0058] According to this embodiment, the first temperature is preferablyabout 37° C. and the second temperature is preferably about 5° C.

[0059] According to this embodiment, the platelets may be stored withinthe preservation medium at a pressure of at least 30 ATM, morepreferably at least 70 ATM, most preferably at least 200 ATM.

[0060] According to this embodiment, the platelets may be stored withinthe preservation medium for at least 3 days, more preferably at least 5days, most preferably at least 7 days. Also according to thisembodiment, the platelets may be stored within the preservation mediumfor between 3 and 20 days, more preferably between 5 and 20 days. Longerstorage of platelets is also possible.

[0061] In regard to all of the compositions of the present invention, itpreferred that at least 65% of the platelets are intact and functionalafter storage, more preferably at least 75% of the platelets, mostpreferably at least 85% of the platelets.

[0062] The gel-forming material preferably constitutes between 0.2% and4% of the preservation medium although the concentration may varydepending on the particular gel-forming material used. Examples ofgel-forming material that may be used include, but are not limited to,gelatin, agarose, agar, pectin, carob cassia and natural or syntheticwater soluble gums. Many of the gel-forming materials are commerciallyavailable. They are typically extracted from natural sources and areoften used as additive to various foods. Examples of water solublepolysaccharide gums include xanthan gum, konjac gum, guar gum, gumarabic, sodium alginate, carrageenan and irgacanth gum. Synthetic watersoluble gel-forming material includes hydroxyethyl methacrylaic.

[0063] The preservation medium may further include an energy source forincreasing hypertonicity of the medium. The energy source preferablyconstitutes between 0 and 5% of the preservation medium, more preferablybetween 0.25 and 5% of the preservation medium, and most preferablybetween 0.5 and 5% of the preservation medium.

[0064] A wide variety of energy sources may be used. Most typically, theenergy source is a carbohydrate, such as a sugar. Particular examples ofenergy sources include glucose, sucrose, mannose, fructose andgalactose. Moreover, sucrose may repair damage in the cell membrane andglucose provides nutrients to sustain cell metabolism in the oxygen-poorconditions caused by the cooling process. Carbohydrates such as sucroseand glucose bind water, thus promoting gel formation and inhibitingosmotic pressure build-up within the platelets.

[0065] The preservation medium may further include water soluble salts.The salt preferably constitute between 0 and 2% of the preservationmedium. Examples of salts include, but are not limited to, sodiumchloride, potassium chloride, magnesium chloride, sodium phosphate,potassium phosphate and sodium gluconate. For example, sodium chlorideprevents hemolysis by inhibiting the flow of water to the plateletsduring cooling. As the platelets are cooled below 20° C., the cytoplasmchanges from a colloid to a gel, and free water leaves the cell. As theplatelets are cooled even further, the hypertonic concentration of NaClprevents water from reentering the platelets. Sodium chloride alsolowers the freezing point of blood plasma by 2.5° C.

[0066] The preservation medium may further include an anticoagulant.Examples of anticoagulants that may be used include heparin, citratedextrose, citrate phosphate dectrose, amantadine, ajoene andticlopidine.

[0067] The preservation medium may further include amino acids. Examplesof amino acids that may be used include arginine, lysine, aspartate andglutamate.

[0068] In a preferred embodiment, the preservation medium includes 1 to3% gelatin. As it is cooled, the gelatin causes solidification of thepreservation medium and the resulted gel matrix forms a physical barrierbetween platelets. Thus, the gel matrix formed suspends cells in thepreservation medium and reduces sedimentation and clumping of platelets.

[0069] In a more preferred embodiment, the preservation solutionincludes 1.0 to 3.0% gelatin, 1.0 to 2.0% glucose, 1.0 to 3.0% sucrose,and 0.2 to 0.6% NaCl.

[0070] 2. Methods for Platelet Storage

[0071] The present invention provides a variety of methods for storingplatelets for direct transfusion into a patient. According to oneembodiment, the method comprises the following steps:

[0072] 1) forming a fluent platelet composition comprising platelets anda preservation medium including plasma and a gel-forming material in aconcentration relative to the plasma such that the medium is in asufficiently fluent state at a first temperature to allow platelets tomove within the medium and is in a sufficiently gelatinous state at asecond, lower temperature to substantially prevent platelets from movingfreely within the medium;

[0073] 2) cooling the fluent preservation medium to form a sufficientlygelatinous state to substantially prevent free movement of the plateletswithin the preservation medium; and

[0074] 3) storing the platelets within the preservation medium in agelatinous state for at least 3 days where at least 50% of the plateletsare intact and functional after the at least 3 days.

[0075] According to this embodiment, the first temperature is preferablyabout 37° C. and the second temperature is preferably about 5° C.,although different first and second temperatures may be employed.

[0076] For example, the platelet composition is formed by suspendingplatelets in the preservation medium that includes a gel-formingmaterial and plasma at about 37° C. The preservation medium is in afluent state so that the platelets can distribute discretely within themedium following moderate agitations. The platelet composition can becooled gradually to about 5° C. where the gel-forming material causesthe preservation medium to become sufficiently gelatinous so as to forma physical barrier between the already distributed platelets. Under suchconditions, platelets are prevented from moving freely within thegelatinous medium and activating upon contacting each other. As aresult, the platelets can be stored for a prolonged period of time andstill maintain their functional integrity.

[0077] According to this embodiment, the platelets may be stored withinthe preservation medium for at least 3 days, more preferably at least 5days and most preferably at least 7 days. Also according to thisembodiment, the platelets may be stored within the preservation mediumfor between 3 and 20 days, more preferably between 5 and 20 days. Longerstorage of platelets is also possible.

[0078] Also according to this embodiment, the platelets may be storedwithin the preservation medium at a temperature less than 10° C. andpreferably between −10° C. and 10° C. In one variation, the plateletsare stored at a temperature between 0° C. and 10° C. at 1 ATM, morepreferably at a temperature between 0° C. and 5° C. at 1 ATM.

[0079] In another embodiment, a method is provided to store platelets atsubzero temperatures and under pressure higher than atmosphericpressure. The method comprises the following steps:

[0080] 1) forming a fluent platelet composition comprising platelets anda preservation medium including plasma and a gel-forming material in aconcentration relative to the plasma such that the medium is in asufficiently fluent state at a first temperature to allow platelets tomove within the medium and is in a sufficiently gelatinous state at asecond, lower temperature to substantially prevent platelets from movingfreely within the medium;

[0081] 2) cooling the fluent preservation medium to form a sufficientlygelatinous state to substantially prevent free movement of the plateletswithin the preservation medium; and

[0082] 3) storing the platelets within the preservation medium in agelatinous state for at least 1 day at a temperature below 0° C. and ata pressure of at least 10 ATM where at least 50% of the platelets areintact and functional after the at least 1 day.

[0083] According to this embodiment, the platelets are preferably storedwithin the preservation medium at a pressure of at least 30 ATM, morepreferably at a pressure of at least 70 ATM, most preferably at apressure of at least 200 ATM.

[0084] In another variation, the platelets are stored within thepreservation medium at a temperature between −10° C. and 0° C. at apressure greater than 10 ATM, more preferably at a temperature between−8° C. and −2° C. at a pressure greater than 10 ATM.

[0085] Also according to this embodiment, the platelets may be storedwithin the preservation medium for at least 3 days, more preferably atleast 5 days, most preferably at least 7 days. Also according to thisembodiment, the platelets may be stored within the preservation mediumfor between 3 and 20 days, more preferably between 5 and 20 days. Longerstorage of platelets is also possible.

[0086] By using these methods, platelets are stored under conditionswhere their metabolism and biochemical reactions slow down and theirfunctional integrity is preserved. The platelet composition stored atlow temperature can be brought to a condition ready for transfusion intoa patient by warming the composition up to about 37° C. where thegel-like composition melts to a sufficiently fluent state.

[0087] 3. Physics of Subzero Pressurized Storage

[0088] Temperature is one of the most important parameters to beconsidered when storing living biological materials. When thetemperature inside a cell drops too low, irreversible biochemical andstructural changes occur. Several hundred biochemical reactions takeplace concurrently in the living cell. The rate of these biochemicalreactions depends on several factors, including pressure, temperature,viscosity of the environment, pH, and concentrations of reactivemolecules.

[0089] A metabolic process typically includes a series of intermediateprocesses, in which a substrate s is converted into a series ofintermediate products X₁, X₂, X₃ . . . before being converted into afinal product P. For each of these intermediate processes, the reactionsmay be catalyzed with different enzymes E₀, E₁, E₂ . . . :$\begin{matrix}{\begin{matrix}E_{0} & E_{1} & E_{2}\end{matrix}\left. S\rightarrow\left. X_{1}\rightarrow\left. X_{2}\rightarrow\left. {X_{3}\quad \ldots}\quad\rightarrow P \right. \right. \right. \right.} & \text{Equation~~(1)}\end{matrix}$

[0090] Under normal conditions, the volume of substrate s transformedper unit of time equals the volume of product P obtained per unit oftime: $\begin{matrix}{{- \frac{\lbrack S\rbrack}{t}} = {+ \frac{\lbrack P\rbrack}{t}}} & \text{Equation~~(2)}\end{matrix}$

[0091] where [s] and [P] are the concentrations of substrate s andproduct P. The concentration of the intermediate products [X₁], [X₂],[X₃] under such conditions should also be constant: $\begin{matrix}{\frac{\left\lbrack X_{1} \right\rbrack}{t} = {\frac{\left\lbrack X_{2} \right\rbrack}{t} = {\frac{\left\lbrack X_{3} \right\rbrack}{t} = 0}}} & \text{Equation~~(3)}\end{matrix}$

[0092] Therefore, for each intermediate product, its rate of formationequals its rate of transformation. The concentrations of eachintermediate product may be expressed in terms of the rates of formationand transformation: $\begin{matrix}{\frac{\left\lbrack X_{3} \right\rbrack}{t} = {{- \frac{\left\lbrack X_{2} \right\rbrack}{t}} = {K_{2} \cdot \left\lbrack X_{2} \right\rbrack}}} & \text{Equation~~(4)}\end{matrix}$

[0093] where K₂ is the constant of rate reaction constant oftransformation of product X₂ and formation of product X₃. For steadystate: $\begin{matrix}{{- \frac{\lbrack S\rbrack}{t}} = {{+ \frac{\left\lbrack X_{1} \right\rbrack}{t}} = {{+ \frac{\left\lbrack X_{2} \right\rbrack}{t}} = {{{+ \frac{\left\lbrack X_{3} \right\rbrack}{t}}\ldots}\quad = {+ \frac{\lbrack P\rbrack}{t}}}}}} & \text{Equation~~(5)}\end{matrix}$

[0094] From the above it follows that:

K ₁ ·[X ₁ ]=K ₂ ·[X ₂] $\begin{matrix}{{\left\lbrack X_{1} \right\rbrack:\left\lbrack X_{2} \right\rbrack} = {K_{2}:K_{1}}} & \text{Equation~~(6)}\end{matrix}$

[0095] Therefore, the concentration of each intermediate product isdetermined by its rate constants of formation and transformation.

[0096] Temperature dependence is defined by constant K of the rate ofchemical reaction to Arrenius: $\begin{matrix}{K = {A \cdot ^{{- E}/{RT}}}} & \text{Equation~~(7)}\end{matrix}$

[0097] where

[0098] A is the constant coefficient in some temperature interval;

[0099] E is the activating energy of chemical reaction per 1 mol of thesubstance;

[0100] R is the universal gas constant; and

[0101] T is the absolute temperature.

[0102] For most biochemical reactions, E>>RT. Taking the naturallogarithm of both sides of Equation (7) gives: $\begin{matrix}{{\ln \quad K} = {\ln \quad A\frac{- E}{RT}}} & \text{Equation~~(8)}\end{matrix}$

[0103]FIG. 1 shows a graph of ln K versus temperature. From 30° C. to37° C., A is constant. For different chemical reactions E and A aredifferent. As temperature decreases, there is a misbalance of reactionsrates and Equation (5) no longer holds. This means the intermediateproduct concentrations corresponding to each of the biochemicalreactions begin to change. This begins breakdown of cell structures,including the cell membrane, and can end in cell death.

[0104] Chemical reactions are either exothermic or endothermic, i.e.they either give off or absorb energy. Reactions taking place duringhydrolysis can release large amounts of energy. The oxidation of 1 molof glucose releases 2883 kJ of energy. Should the biochemical reactionrates slow down too much, irreversible process begin to take placefinally leading to total destruction of the cell. Therefore, coefficientA becomes a function of temperature T.

[0105] As the temperature drops below 20° C., the lipid bi-layer of thecell membrane undergoes a phase transmission from a colloid to a gel.The viscosity of a gel is much higher then that of its colloid.Consequently, rates of diffusion and active transportation of moleculesthrough the cell membrane decrease sharply, resulting in a slowing downof the rate of biochemical reactions in a cell. As a result of the phasetransformation of the cell membrane, the surface area of the lipidbi-lay surface and cell size reduce considerably due to the loss ofwater from the cell.

[0106] As the density of osmo-active substances increases, watermolecules return to the cell thereby increasing osmotic pressure.Membrane tension reaches a critical point and may lose its barrierfunction. Membrane damage develops, resulting in morphological andstructural changes, as well as loss of the ability for activeadaptation.

[0107] As the temperature drops below 8° C., the cell cytoplasmundergoes a phase transformation into a gel. At this temperature, thereis a sharp decrease in diffusion rate and active transportation ofmolecules, as well as in biochemical reaction rates.

[0108] As the temperature falls below −3° C., water crystallizationbegins to occur both inside and outside the cell. In the absence ofcryoprotectors, water crystallization outside the cell leads to celldehydration, decreased cell size, and increased concentrations of saltand other substances inside the cell. Water crystallization inside thecell results in structural cell membrane destruction.

[0109]FIG. 2 shows the phase transition lines for plasma and a 2.5% NaClsolution. At normal pressures, plasma freezes at −2.5° C. Plasmacontains various chemical which lower the freezing point by interferingwith the formation of the crystal lattice structure of ice. Cellstructures can be cooled to −4° C. to −3° C. without watercrystallization into cytoplasm. At normal pressures, the 2.5% NaClsolution freezes at −1.7° C.

[0110]FIG. 3 shows the phase transition lines for water and a 2.5% NaClsolution. The addition of NaCl to water as lowers the freezing point,and thus allows lower temperatures to be achieved for a given pressure.The line shows one example of how a biological material may be subjectedto a combination of high pressure and low temperature to preventfreezing.

[0111] 4. Apparatus for Subzero Pressurized Storage

[0112] The present invention also provides apparatuses for the extendedstorage of biological materials, and, in particular, platelets. Forexample, the apparatuses can be used to store platelets suspended in apreservation medium comprising plasma and a gel-forming material in aconcentration relative to the plasma such that the medium is in asufficiently fluent state at about 37° C. to allow platelets to movewithin the medium and is in a sufficiently gelatinous state at about 5°C. to substantially prevent platelets from moving freely within themedium.

[0113]FIG. 4 shows an assembled view of one embodiment of a biologicalmaterial preservation apparatus 100 of the present invention.Preservation apparatus 100 includes a chamber 110 and a cover 130.

[0114] FIGS. 5A-5B show side cutaway and top views, respectively, ofchamber 110. Chamber 110 includes a mouth 111 and a lip 112. Lip 112includes an inside surface 113 and a top surface 114. Inside surface 113and top surface 114 meet at a first radius r₁. Top surface 114 includesa channel 115. Channel 115 may have a sealing device 116 seated at abottom of channel 115, such as an O-ring or rubber gasket. Chamber 110may be manufactured in different sizes to accommodate a platelet bag,blood donation bag, heart, liver, kidney, or other bags and biologicalmaterials.

[0115]FIG. 6 shows a cutaway view of cover 130. Cover 130 is configuredto mate with and seal chamber 110. Cover 130 includes a bottom surface131. Bottom surface 131 includes a protrusion 132 and a sealingstructure 133. Bottom surface 131 and protrusion 132 meet at a secondradius r₂. Protrusion 132 is inserted into mouth 111 of chamber 110 whencover 130 is mated with chamber 110. Protrusion 132 includes a sidesurface 134. Side surface 134 of protrusion 132 and inside surface 113of lip 112 define a first gap 140 and are substantially parallel whencover 130 is mated with chamber 110. Bottom surface 132 of cover 130 andtop surface 118 of lip 114 define a second gap 141 and are substantiallyparallel when cover 130 is mated with chamber 110. Second gap 141 has alength greater than a width of first gap 140. Sealing structure 133 isinserted into channel 115 of lip 112 when cover 130 is mated withchamber 110.

[0116] Cover 130 may be made to be a spherical section, which allowscover 130 to be made lighter and with less material than a flat cover130 without sacrificing strength. When preservation apparatus 100 isfilled with, for example, saline solution and then cooled below thefreezing point, ice will begin to form along the walls of chamber 110and cover 130. Ice will form in first gap 140 and second gap 141 andhelp to seal chamber 110. Thus, the high pressures within chamber 110are largely borne by this ice seal, thus minimizing the need to makechannel 115, sealing device 116, and sealing structure 133 extremelyrobust and capable of withstanding such high pressures. Channel 115,sealing device 116, and sealing structure 133 only need to withstandpressures of up to 10 atm before the ice seal takes over. The sizes offirst gap 140 and second 141 are not critical, but may be minimized sothat ice fills them before the seal is subjected to pressures above 10atm. In one embodiment, first gap 140 and second gap 141 may be lessthan 2.0 mm in width. Chamber 110 includes a suspension device 117 whichprevents biological material or bag placed within pressure chamber fromcoming into contact with the walls of chamber 110. Suspension device 117may be a net, a platform, a spacer, or any other suitable device. Cover130 may be designed to be sealed to chamber 110 directly, or with theaid of a cover retaining device 135. Cover retaining device 135 may bedesigned to allow cover 130 to be installed and removed quickly andeasily. Cover retaining device 135 may be coupled to chamber 110 via abayonet-style connection, threads, or any other suitable couplingmethod. Cover retaining device 135 may include a centering pin 136 tokeep cover retaining device 135 centered or attached to cover 130. Coverretaining device 135 may also include holes 137 to allow a wrench orother tool to be used with cover retaining device 135. Cover retainingdevice 135 may be produced in two separated pieces to simplifymanufacturing. FIGS. 7A-7C show cutaway and top views of a two-piececover retaining device 135.

[0117] Preservation apparatus 100 may include a pressure gauge 150 withan elastic membrane 151 placed within chamber 110. Pressure gauge 150may include a relief valve 152 which prevents pressure withinpreservation apparatus 100 from exceeding a predetermined maximum.

[0118] By utilizing the features of the present invention, the followingobjectives for preserving biological materials, in particular,platelets, are achieved:

[0119] 1. Mechanically suspending the biological materials in apreservation medium.

[0120] 2. Storing the biological materials at the lowest possibletemperature while maintaining them in a liquid state. Under theseconditions, the rate of biochemical reactions are relatively slow andtherefore, the rates of change in the concentrations of intermediateproducts is small.

[0121] 3. Slowly cooling solutions with platelets to allow free and safewater flow from the cell to prevent membrane tension from reaching abursting point during the phase transmission from a colloid to a gel. Onthe other hand, the cooling rate should be high enough to preventintermediate biochemical reactions from causing irreversible changes incell structure.

EXAMPLES

[0122] 1. Method of Platelet Preservation

[0123] The following is one example of the method of the presentinvention for preserving blood platelets. Heparin may be used as ananticoagulant before this process is begun.

[0124] (1) Mix the platelets with a preservation solution of 2.9%gelatin, 0.44% sucrose, 1.17% glucose, and 0.49% NaCl.

[0125] (2) Seal the platelets and preservation solution into a storagebag, making sure that any air has been pumped out The storage bag may beany standard platelet storage bag such as a flexible silicone rubberbag.

[0126] (3) Cool the platelets and preservation solution to 15° C. within1 hour. Continuous agitation is required until the preservation solutionbecomes a gel.

[0127] (4) Cool the storage bag to 6° C. to 8° C. within 1 to 1.5 hours.

[0128] (5) Cool the preservation apparatus to 6° C. to 8° C.

[0129] (6) Insert the storage bag into the preservation apparatus usingthe suspension device.

[0130] (7) Fill the preservation apparatus with a pressure transferfluid of 2.5% NaCl solution.

[0131] (8) Seal the preservation apparatus, making sure it is completelyfull and no air is trapped inside.

[0132] (9) Cool the preservation apparatus to −7.5±0.2° C. within 1.5 to2 hours. The pressure transfer fluid is a fluid which expands whencooled or frozen, and thus will be able to exert a pressure upon the bagwithin the substantially fixed volume of the preservation apparatus.With the 2.5% NaCl solution, the water will begin to freeze at the wallsof the pressure chamber. As the ice is formed at the walls of thepressure chamber, the expansion will create the high pressures requiredwithin the preservation apparatus, which will be transferred by theunfrozen fluid immediately surrounding the storage bag to the storagebag. The NaCl lowers the freezing point of the pressure transfer fluid,thus allowing the low temperatures required to be achieved before theentire volume of the pressure transfer fluid becomes frozen. Thepreservation solution has a lower freezing point than the pressuretransfer fluid. The pressure inside the preservation apparatus will riseto 500 atm. As ice begins to form, pressure within the preservationapparatus will increase because ice and water are essentiallynon-compressible. The relationship between temperature and pressure hereis consistent and predictable. The combination of the preservationsolution, the high storage pressure, and the low storage temperatureallows the platelets to be stored for up to 15 days. Erythrocytes may bestored up to 30 days and leukocytes up to 22 days using this method.

[0133] (10) When the platelets are needed for use, allow thepreservation apparatus to thaw completely at room temperature,approximately 20° C., before opening the preservation apparatus. Becausethe components in the preservation solution are all nontoxic, theplatelets may be used immediately without further preparation.

[0134] 2. Studies of Platelet Survival

[0135] Human blood platelets suspended in plasma and contained instandard platelet bags were mixed with a concentrated gelatin stocksolution at 37° C. The concentrated gelatin stock solution alsocontained sugar and sodium chloride. Typically, the amount of gelatinsolution added was ¼ the volume of plasma. For example, 25 ml of agelatin stock solution containing 3.5% gelatin and 10% glucose was addedto 100 ml of plasma with platelets, resulting in a final solution at0.7% gelatin and 2% glucose. The final concentration of platelets in theplatelet bag is about 300,000 per μl.

[0136] The platelet compositions were stored at a refrigeratortemperature or in an preservation apparatus according to the presentinvention at subzero temperatures. Following certain periods of time (ndays) storage, the platelet compositions were warmed to about 37° C. andanalyzed for post-storage (D_(n)) activity, such as plateletaggregation, as compared to the activity of platelets before storage(D₀) by using standard methods performed by hospital clinicallaboratories.

[0137] Typically, platelet aggregation is performed by adding astimulus, such as 10 μM adenosine diphosphate (ADP) and 14 μgristocetin, to a suspension of platelets in a curvette or on a slide.Methods and amounts of stimuli typically used are well known to thoseskilled in the art. The stimulating agent binds to receptors on theplatelets and causes the platelets to release substances from granulesand initiates a cascade of events resulting in platelets binding to eachother and falling out of the suspension. Typically, the aggregation ofplatelets is indicated by an increased ability of the solution to allowpassage of light (increased % transmission or decreased turbidity). Thetime platelets respond to each stimulus was recorded in seconds. Thesurvival rate of platelets was measured by counting post-storageplatelets with intact morphology under a microscope and comparing withthe platelets before the storage.

[0138] Table I lists the constituents of the preservation medium, thesurvival rates of the platelets and aggregation response times of theplatelets when exposed to ristocetin or ADP and after the platelets havebeen stored in preservation media for a listed period of time (n days)at a refrigerator temperature 4° C. TABLE I Aggregation Response (sec.)Gelatin Sucrose Glucose NaCl n days at 4° C. Survival Ristocetin(D_(o)/D_(n)) ADP (D_(o)/D_(n)) 0.45% 2.0% 2.0% 0.5% 5 d 82% 9/7 9/80.7% 2.0% 2.0% 0.5% 5 d 100% 14/7  11/7  1.5% 2.0% 2.0% 0.5% 5 d 88%14/12 17/12

[0139] Table II lists the constituents of the preservation medium, thesurvival rates of the platelets and aggregation response times of theplatelets when exposed to ristocetin and adenosine diphosphate (ADP)after the platelets have been stored in preservation media for a listedperiod of time at a sub-zero temperature (−4 to −10° C.). TABLE IIAggregation Response (sec.) Gelatin Sucrose Glucose NaCl n days at <0°C. Survival Ristocetin (D₀/D_(n)) ADP (D₀/D_(n)) Plasma  5d  6% 11/23 11/43 1.5% 0.5% 1.0% 0.5%  5d 100% 11/8   12/10 3.0% 0.5% 1.0% 0.5%  5d100% 11/6  12/7 0.5% 0.5% 1.0% 0.5%  5d  76% 9/9  9/10 1.5% 2.0% 1.0%0.5%  5d 100% 11/8  10/9 1.5% 1.5% 1.0% 0.5%  5d 100%  9/14  10/17 0.7%2.0% 2.0% 0.5% 11d  45%  9/10  10/13 1.5% 2.0% 2.0% 0.5% 11d >50% 9/811/8 0.7% 2.0% 2.0% 0.5% 13d  86% 9/4 10/7 1.5% 2.0% 2.0% 0.5% 13d 100%11/6  14/5

[0140] As can be seen from the results shown in Table I and II,platelets were stored for five or more days with high survival rates.

[0141] The foregoing description of the invention has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise forms disclosed.Many modifications and variations will be apparent. It is intended thatthe scope of the invention be defined by the following claims and theirequivalents.

1. A platelet composition suitable for direct transfusion into a patientcomprising: a preservation medium comprising plasma and a gel-formingmaterial in a concentration relative to the plasma such that the mediumis in a sufficiently fluent state at a first temperature to allowplatelets to move within the medium and is in a sufficiently gelatinousstate at a second, lower temperature to substantially prevent plateletsfrom moving freely within the medium; and platelets which have beenstored within the preservation medium in a gelatinous state for at least3 days where at least 50% of the platelets are intact and functionalafter the at least 3 days.
 2. The platelet composition according toclaim 1, wherein the first temperature is about 37° C. and the secondtemperature is about 5° C.
 3. The platelet composition according toclaim 1, wherein the platelets are stored within the preservation mediumfor at least 5 days where at least 50% of the platelets are intact andfunctional after the at least 5 days.
 4. The platelet compositionaccording to claim 1, wherein the platelets are stored within thepreservation medium for between 3 and 20 days where at least 50% of theplatelets are intact and functional after the at least 3 and 20 days. 5.The platelet composition according to claim 1, where the platelets arestored for the at least 3 days within the preservation medium at atemperature less than 10° C.
 6. The platelet composition according toclaim 1, where the platelets are stored for the at least 3 days withinthe preservation medium at a between −10° C. and 10° C.
 7. The plateletcomposition according to claim 1, where the platelets are stored for theat least 3 days within the preservation medium at a temperature between0° C. and 10° C. at 1 ATM.
 8. The platelet composition according toclaim 1, where the platelets are stored for the at least 3 days withinthe preservation medium at a temperature between 0° C. and 5° C. at 1ATM.
 9. The platelet composition according to claim 1, where theplatelets are stored for the at least 3 days within the preservationmedium at a temperature less than 5° C.
 10. The platelet compositionaccording to claim 1, where the platelets are stored for the at least 3days within the preservation medium at a temperature between −10° C. and0° C. at a pressure greater than 10 ATM.
 11. The platelet compositionaccording to claim 1, where the platelets are stored for the at least 3days within the preservation medium at a temperature between −8° C. and−2° C. at a pressure greater than 10 ATM.
 12. The platelet compositionaccording to claim 1, where at least 65% of the platelets are intact andfunctional after the at least 3 days.
 13. The platelet compositionaccording to claim 1, where at least 75% of the platelets are intact andfunctional after the at least 3 days.
 14. The platelet compositionaccording to claim 1, where at least 85% of the platelets are intact andfunctional after the at least 3 days.
 15. The platelet compositionaccording to claim 1, wherein the gel-forming material constitutesbetween 0.2% and 4% of the preservation medium.
 16. The plateletcomposition according to claim 1, wherein the gel-forming material isselected from the group consisting of gelatin, agarose, agar, pectin,carob cassia, xanthan gum, konjac gum, guar gum, gum arabic, sodiumalginate, carrageenan, irgacanth gum and hydroxyethyl methacrylaic. 17.The platelet composition according to claim 1, wherein the preservationmedium further includes an energy source.
 18. The platelet compositionaccording to claim 17, wherein the energy source constitutes between 0and 5% of the preservation medium.
 19. The platelet compositionaccording to claim 17, wherein the energy source includes acarbohydrate.
 20. The platelet composition according to claim 17,wherein the energy source includes a sugar selected from the groupconsisting of glucose, sucrose, mannose, fructose and galactose.
 21. Theplatelet composition according to claim 1, wherein the preservationmedium further includes one or more anticoagulants.
 22. The plateletcomposition according to claim 21, wherein the anticoagulant is selectedfrom the group consisting of heparin, citrate dextrose, citratephosphate dextrose, amantadine, ajoene and ticlopidine.
 23. A plateletcomposition suitable for direct transfusion into a patient comprising: apreservation medium comprising plasma and a gel-forming material in aconcentration relative to the plasma such that the medium is in asufficiently fluent state at about 37° C. to allow platelets to movewithin the medium and is in a sufficiently gelatinous state at about 5°C. to substantially prevent platelets from moving freely within themedium; and platelets.
 24. A platelet composition suitable for directtransfusion into a patient comprising: a preservation medium comprisingplasma and a gel-forming material in a concentration relative to theplasma such that the medium is in a sufficiently fluent state at about37° C. to allow platelets to move within the medium and is in asufficiently gelatinous state at about 5° C. to substantially preventplatelets from moving freely within the medium; and platelets storedwithin the preservation medium for at least 1 day at a pressure of atleast 10 ATM and a temperature below 0° C. where at least 50% of theplatelets are intact and functional after the at least 1 day.
 25. Theplatelet composition according to claim 24, wherein the platelets arestored within the preservation medium at a pressure of at least 70 ATM.26. The platelet composition according to claim 24, wherein theplatelets are stored within the preservation medium at a pressure of atleast 200 ATM.
 27. The platelet composition according to claim 24,wherein the platelets are stored within the preservation medium for atleast 3 days where at least 50% of the platelets are intact andfunctional after the at least 3 days.
 28. The platelet compositionaccording to claim 24, wherein the platelets are stored within thepreservation medium for at least 5 days where at least 50% of theplatelets are intact and functional after the at least 5 days.
 29. Theplatelet composition according to claim 24, wherein the platelets arestored within the preservation medium for between 3 and 20 days where atleast 50% of the platelets are intact and functional after the at least3 and 20 days.
 30. The platelet composition according to claim 24, whereat least 65% of the platelets are intact and functional after the atleast 3 days.
 31. The platelet composition according to claim 24, whereat least 75% of the platelets are intact and functional after the atleast 3 days.
 32. The platelet composition according to claim 24, whereat least 85% of the platelets are intact and functional after the atleast 3 days.
 33. The platelet composition according to claim 24,wherein the gel-forming material constitutes between 0.2% and 4% of thepreservation medium.
 34. The platelet composition according to claim 24,wherein the gel-forming material is selected from the group consistingof gelatin, agarose, agar, pectin, carob cassia, xanthan gum, konjacgum, guar gum, gum arabic, sodium alginate, carrageenan, irgacanth gumand hydroxyethyl methacrylaic.
 35. The platelet composition according toclaim 24, wherein the preservation medium further includes an energysource.
 36. The platelet composition according to claim 35, wherein theenergy source constitutes between 0 and 5% of the preservation medium.37. The platelet composition according to claim 35, wherein the energysource includes a carbohydrate.
 38. The platelet composition accordingto claim 35, wherein the energy source includes a sugar selected fromthe group consisting of glucose, sucrose, mannose, fructose andgalactose.
 39. The platelet composition according to claim 24, whereinthe preservation medium further includes one or more anticoagulants. 40.The platelet composition according to claim 39, wherein theanticoagulant is selected from the group consisting of heparin, citratedextrose, citrate phosphate dextrose, amantadine, ajoene andticlopidine.
 41. A method for storing platelets for direct transfusioninto a patient comprising: forming a fluent platelet compositioncomprising platelets and a preservation medium including plasma and agel-forming material in a concentration relative to the plasma such thatthe medium is in a sufficiently fluent state at a first temperature toallow platelets to move within the medium and is in a sufficientlygelatinous state at a second, lower temperature to substantially preventplatelets from moving freely within the medium; cooling the fluentpreservation medium to form a sufficiently gelatinous state tosubstantially prevent free movement of the platelets within thepreservation medium; and storing the platelets within the preservationmedium in a gelatinous state for at least 3 days where at least 50% ofthe platelets are intact and functional after the at least 3 days. 42.The method according to claim 41, wherein the first temperature is about37° C. and the second temperature is about 5° C.
 43. The method forstoring platelets according to claim 41, wherein the platelets arestored within the preservation medium for at least 5 days where at least50% of the platelets are intact and functional after the at least 5days.
 44. The method for storing platelets according to claim 41,wherein the platelets are stored within the preservation medium for atleast 7 days where at least 50% of the platelets are intact andfunctional after the at least 7 days.
 45. The method for storingplatelets according to claim 41, wherein the platelets are stored withinthe preservation medium for between 3 and 20 days where at least 50% ofthe platelets are intact and functional after the at least 3 and 20days.
 46. The method for storing platelets according to claim 41,wherein the platelets are stored for the at least 3 days within thepreservation medium at a temperature less than 10° C.
 47. The method forstoring platelets according to claim 41, wherein the platelets arestored for the at least 3 days within the preservation medium at abetween −10° C. and 10° C.
 48. The method for storing plateletsaccording to claim 41, wherein the platelets are stored for the at least3 days within the preservation medium at a temperature between 0° C. and10° C. at 1 ATM.
 49. The method for storing platelets according to claim41, wherein the platelets are stored for the at least 3 days within thepreservation medium at a temperature between 0° C. and 5° C. at 1 ATM.50. The method for storing platelets according to claim 41, where theplatelets are stored for the at least 3 days within the preservationmedium at a temperature less than 5° C.
 51. The method for storingplatelets according to claim 41, where the platelets are stored for theat least 3 days within the preservation medium at a temperature between−10° C. and 0° C. at a pressure greater than 10 ATM.
 52. The method forstoring platelets according to claim 41, where the platelets are storedfor the at least 3 days within the preservation medium at a temperaturebetween −8° C. and −2° C. at a pressure greater than 10 ATM.
 53. Amethod for storing platelets for direct transfusion into a patientcomprising: forming a fluent platelet composition comprising plateletsand a preservation medium including plasma and a gel-forming material ina concentration relative to the plasma such that the medium is in asufficiently fluent state at a first temperature to allow platelets tomove within the medium and is in a sufficiently gelatinous state at asecond, lower temperature to substantially prevent platelets from movingfreely within the medium; cooling the fluent preservation medium to forma sufficiently gelatinous state to substantially prevent free movementof the platelets within the preservation medium; and storing theplatelets within the preservation medium in a gelatinous state for atleast 1 day at a temperature below 0° C. and at a pressure of at least10 ATM where at least 50% of the platelets are intact and functionalafter the at least 1 day.
 54. The method according to claim 53, whereinthe first temperature is about 37° C. and the second temperature isabout 5° C.
 55. The method for storing platelets according to claim 53,wherein the platelets are stored within the preservation medium at apressure of at least 70 ATM.
 56. The method for storing plateletsaccording to claim 53, wherein the platelets are stored within thepreservation medium at a pressure of at least 200 ATM.
 57. The methodfor storing platelets according to claim 53, wherein the platelets arestored within the preservation medium for at least 3 days where at least50% of the platelets are intact and functional after the at least 3days.
 58. The method for storing platelets according to claim 53,wherein the platelets are stored within the preservation medium for atleast 5 days where at least 50% of the platelets are intact andfunctional after the at least 5 days.
 59. The method for storingplatelets according to claim 53, wherein the platelets are stored withinthe preservation medium for at least 7 days where at least 50% of theplatelets are intact and functional after the at least 7 days.
 60. Themethod for storing platelets according to claim 53, wherein theplatelets are stored within the preservation medium for between 3 and 20days where at least 50% of the platelets are intact and functional afterthe at least 3 and 20 days.
 61. The method for storing plateletsaccording to claim 53, wherein at least 65% of the platelets are intactand functional after the at least 3 days.
 62. The method for storingplatelets according to claim 53, wherein at least 75% of the plateletsare intact and functional after the at least 3 days.
 63. The method forstoring platelets according to claim 53, wherein at least 85% of theplatelets are intact and functional after the at least 3 days.